By Laila Bassam BEIRUT, March 5 (Reuters) - Rival Lebanese leaders could reach a deal this week to end a political crisis which has sparked the country's worst civil unrest since the 1975-1990 civil war, a senior opposition source said on Monday. The opposition, including Syrian allies Hezbollah and Amal, have been locked in a power struggle for months with the anti-Syrian governing coalition. "The atmosphere is more than positive. Matters are going towards an agreement on a solution," the opposition source, speaking on condition of anonymity, told Reuters, adding that the deal could be concluded this week. A source from the ruling majority also described the atmosphere as positive but said nothing had been finalised. The opposition source said a Saudi-Iranian summit on Saturday had led to the breakthrough in the standoff, which has fuelled tensions between Sunni Muslims loyal to majority leader Saad al-Hariri and Shi'ites who support Hezbollah and Amal. Saudi Arabia's Sunni Muslim leadership backs the government while Iran's Shi'ite Islamist government is a main supporter of Shi'ite Muslim Hezbollah. TRIBUNAL PLANS Under the deal, the opposition source said the sides would form committees to agree on the main points of dispute -- an international tribunal to try suspects in the killing of Rafik al-Hariri and the opposition's demand for a veto in government. The committees would agree on changes to plans for the tribunal and on an expansion of cabinet giving the opposition veto power by allocating it more than a third of the seats. The governing coalition, which is also backed by Western governments, has so far refused to yield to this demand, saying it would give Syria and Iran more influence in Lebanon. The international tribunal to try suspects in the Hariri killing is a priority for Saad al-Hariri, Rafik al-Hariri's son and political heir. The assassination in 2005 triggered international pressure on Syria to withdraw troops from Lebanon. Saad al-Hariri and his allies have accused the opposition of aiming to derail plans for the international tribunal to defend Syria, which they accuse of Hariri's assassination and other attacks on anti-Syrian figures. Damascus denies involvement. The Lebanese opposition, which includes Christian leader Michel Aoun, has stated its support for the idea of a tribunal but demanded a debate on the mandate. The opposition has been camped out in central Beirut near the government's headquarters for more than three months to press its demands. Saudi Arabia's Beirut ambassador Abdelaziz Khojah is shuttling between the Lebanese factions. "I am certain that there is a positive atmosphere and certain that all the parties are striving to find the appropriate way out and the appropriate solution," he told reporters. (Additional reporting by Nadim Ladki)
